Quantization, String Theory

[lmf]

@alanforr

From DD’s point of view a partially quantum mechanical theory is one in which you start from a classical theory and then apply a procedure called quantization to get a quantum theory.

I think that’s a reasonable definition.

Then I assume that a fully (partially) quantum mechanical entity is defined to be an entity that plays a significant role in a fully (partially) quantum mechanical theory?

If so, I think that definition is consistent with the implicit definition of the term I was using when I wrote this paragraph:

I don’t know exactly what a “fully quantum mechanical” entity is, but I don’t think that the particles in QFT count (nor do I think strings or branes count, but that’s a more complicated discussion). Particles arise when you try to write your path integral as an asymptotic series in ħ, so the assumption that quantum effects are small is built into the whole formalism of perturbative QFT.

Spelling it out explicitly:

1. Perturbative QFT (=summing over Feynman diagrams) is not a fully quantum mechanical theory, because it is obtained by applying a procedure called quantization to a classical theory
2. Particles in QFT are edges in Feynman diagrams
3. Therefore, particles in QFT are not fully quantum mechanical entities

Do you agree with 3. now?